feat(community): establish contributor foundation - #3

Tracking

• Repository Issue: Build shared GitHub contributor foundation #2
• Canonical task: https://github.com/codegeist-ai/codegeist/blob/feat/contributor-foundation/docs/tasks/T010_build-shared-github-contributor-foundation/task.md

Summary

Establish the core repository contributor baseline with 0BSD licensing, deterministic JVM CI, safe configuration examples, public task guidance, and license-complete release artifacts.

Verification

• CODEGEIST_TEST_PROVIDER_CATEGORY=remote_paid TEST=LocalOllamaProviderIT DOCKER_HOST=tcp://127.0.0.1:1 task cli:check (202 tests, 6 expected skips)
• Focused example and license tests
• Linux native archive smoke with license hash verification
• Workflow, POM, PowerShell, Bash, and whitespace validation

Impact Checklist

• No credentials, tokens, sensitive configuration, or private security details are included.
• Security implications and private reporting guidance were reviewed.
• Documentation and tests are updated.
• GitHub release artifacts now include LICENSE.
• Shared-kit gitlinks are unchanged.
• Contributions are accepted under 0BSD without CLA or DCO.